Process-microstructure-electrical conductivity relationships in injection-molded polypropylene/carbon nanotube nanocomposite foams

Foam injection molding experiments were conducted to establish the relationships between process, microstructure and electrical conductivity in polypropylene-multiwalled carbon nanotube nanocomposites. The effects of injection flow rate, gas content, melt temperature, void fraction, and cavity location on the microstructure and conductivity were investigated. At optimum processing conditions, foams with cellular skin and core regions were obtained whose conductivity was 6 orders of magnitude higher than that in their solid counterparts. The conductivity was proportionally increased with the injection flow rate, while it was maximized at optimal values of gas content (0.3%), melt temperature (200 °C), and void fraction (30%). Also, a consistently low conductivity was found near the gate location. The conductivity variations were explained in term of the changes that the processing conditions induced to the microstructure and cellular morphology of the skin and core regions. The results of this work find importance in the development of lightweight conductive materials.